Weil McClain Boiler occasionally NOT Starting Up

[bluefleetwood]

Hi guys,
I have an 18 year old Weil McClain Gold Series Gas Boiler that will occasionally make several attempts at calling for fire up. I hear and see it cycling, but the burners don't light. I see the flue damper open and then close again so that seems ok. The Air handlers run, naturally, but of course blowing cold air. And of course the hot water zone will eventually run low. Could this be an electrical/control issue. When I manually toggle the Emergency shut off switch from either location, at the boiler or the top of the stairs, the unit then works fine. Could it be a bad relay in the control box? When it is trying to run, you could see the boiler water temp is very low. Naturally when she fires up the temp rises fine. Any ideas? Thanks!

 

[Sylvan]

Sounds like a relay holding contact . Also a possible spill switch problem

 

[Sponsor]

 

[bluefleetwood]

Sounds like a relay holding contact . Also a possible spill switch problem

Should I just play it safe and replace all the zone relays? It really doesn't matter which of the 3 zones calls for heat. It still gets hung up. Is there a way of bypassing the spill switch to check to see if this is the issue?
Thank you

 

[Dana]

The zone relays would not keep the boiler from firing unless all three were bad (not likely).

The spill switch shipped with current Weil-Mclain's has a red reset button on it, which would tell you right away if that's the issue.

It should be mounted to the draft hood- see item #4 in the diagram on p.3 of the installation manual.

Bypassing the spill switch is theoretically possible, but if it's tripping (or even if it isn't) verifying that there isn't the vent drafting problem is worth doing every year or so. A bird's nest, asphyxiated raccoon carcass, spalling masonry or other blockage can make the drafting marginal, especially when the flue is cold.

Is this thing vented into a masonry chimney on an exterior wall?

Does it have a right sized flue liner for the BTU output of the boiler?

If the boiler is reasonably right-sized for the actual heat load and has the right size flue the duty cycle would be high enough that the flue would stay warm enough to always draft well during cold weather.

A hydro-air handlers can be controlled with a retrofit aquastat in series with the power to inhibit the blower from running when the entering water at the coil plumbing is too cool. This isn't just a comfort issue. If it's not getting at least 150F entering water temp the water it's sending back to the boiler is colder than a cast iron boiler can tolerate, risking corrosive condensation on the boiler's heat exchanger plates.

 

[bluefleetwood]

The zone relays would not keep the boiler from firing unless all three were bad (not likely).

The spill switch shipped with current Weil-Mclain's has a red reset button on it, which would tell you right away if that's the issue.

It should be mounted to the draft hood- see item #4 in the diagram on p.3 of the installation manual.

Bypassing the spill switch is theoretically possible, but if it's tripping (or even if it isn't) verifying that there isn't the vent drafting problem is worth doing every year or so. A bird's nest, asphyxiated raccoon carcass, spalling masonry or other blockage can make the drafting marginal, especially when the flue is cold.

Is this thing vented into a masonry chimney on an exterior wall?

Does it have a right sized flue liner for the BTU output of the boiler?

If the boiler is reasonably right-sized for the actual heat load and has the right size flue the duty cycle would be high enough that the flue would stay warm enough to always draft well during cold weather.

A hydro-air handlers can be controlled with a retrofit aquastat in series with the power to inhibit the blower from running when the entering water at the coil plumbing is too cool. This isn't just a comfort issue. If it's not getting at least 150F entering water temp the water it's sending back to the boiler is colder than a cast iron boiler can tolerate, risking corrosive condensation on the boiler's heat exchanger plates.

I don't think it's the spill switch because when I toggle the EM switch, the system fires up. If the spill switch were tripped, doesn't have to be reset manually? Also, I've had to remove it from the vent hood because it was tripping regularly. It is just hanging alongside the boiler still in series circuit.

 

[Dana]

I don't think it's the spill switch because when I toggle the EM switch, the system fires up. If the spill switch were tripped, doesn't have to be reset manually? Also, I've had to remove it from the vent hood because it was tripping regularly. It is just hanging alongside the boiler still in series circuit.

Dude- that's a SAFETY device that you defeated by pulling it off the draft hood! If the fire alarm kept going off would you just figure out a way to defeat it too?

The spill switch is probably not the cause of your current shut-down problem but if it was "... tripping regularly..." it's a HUGE cause for concern! Whatever else you do, put the spill switch back where it belongs, and fix the venting problems that's causing it to trip.

If fixing the venting problem turns out to be expensive (it usually isn't), even though it probably still has a decade of life left in it, replacing the boiler with a cheap direct vented condensing boiler big enough for your air handlers might be worth it. To even begin to assess that that, start with a fuel-use based heat load calculation, then a room by room Manual-J or IBR load calculation on each zone. The model number(s) of the air handlers and the amount of baseboard in the other zone would be needed too. With a bit of napkin-math it's possible to determine the water temps needed to cover the design load, and whether that would yield condensing in the boiler. It's almost always the case (but it needs to be verified) that hydro-air handlers can still deliver design day heat at condensing temperatures, and that cast iron boilers driving hydro-air are way oversized for the actual heating loads- the boiler needs to oversized to prevent too-cool return water from destroying the boiler from condensation. That ultimately ends up cutting into the as-used AFUE efficiency.

 

[bluefleetwood]

Dude- that's a SAFETY device that you defeated by pulling it off the draft hood! If the fire alarm kept going off would you just figure out a way to defeat it too?

The spill switch is probably not the cause of your current shut-down problem but if it was "... tripping regularly..." it's a HUGE cause for concern! Whatever else you do, put the spill switch back where it belongs, and fix the venting problems that's causing it to trip.

If fixing the venting problem turns out to be expensive (it usually isn't), even though it probably still has a decade of life left in it, replacing the boiler with a cheap direct vented condensing boiler big enough for your air handlers might be worth it. To even begin to assess that that, start with a fuel-use based heat load calculation, then a room by room Manual-J or IBR load calculation on each zone. The model number(s) of the air handlers and the amount of baseboard in the other zone would be needed too. With a bit of napkin-math it's possible to determine the water temps needed to cover the design load, and whether that would yield condensing in the boiler. It's almost always the case (but it needs to be verified) that hydro-air handlers can still deliver design day heat at condensing temperatures, and that cast iron boilers driving hydro-air are way oversized for the actual heating loads- the boiler needs to oversized to prevent too-cool return water from destroying the boiler from condensation. That ultimately ends up cutting into the as-used AFUE efficiency.

So I should First, get a chimney guy here to make sure the exhaust leaving is free and clear. I have had my doubts for some time now as there is water that leaks from the wall where the vent enters. Also, I have replaced the Spill Switch some time ago from the push button reset to an automatic. Am I resetting that when I cycle the Emergency Toggle Switch? Plus if it's just hanging off to the side, what would make it trip in the first place? Could the thermocouple be on its way? Thanks so much for the help.

 

[NY_Rob]

Blue.... it honestly sounds like it's something you should not be attempting to diagnose/repair yourself at this point.
You could do some serious damage, hurt yourself or your family.

Give Robert O'Brien a call, he's in your neighborhood, he's top notch and honest!

Technical Heating
78 CHESTNUT ST
MOUNT SINAI, NY 11766

Robert O'Brien
Phone 631-473-1597

 

[bluefleetwood]

Blue.... it honestly sounds like it's something you should not be attempting to diagnose/repair yourself at this point.
You could do some serious damage, hurt yourself or your family.

Give Robert O'Brien a call, he's in your neighborhood, he's top notch and honest!

Technical Heating
78 CHESTNUT ST
MOUNT SINAI, NY 11766

Robert O'Brien
Phone 631-473-1597

OUTSTANDING!!!!!!!!!!!!!!!!!!! Thank you very much!!!!!!

 

[bluefleetwood]

OUTSTANDING!!!!!!!!!!!!!!!!!!! Thank you very much!!!!!!

Thanks again for the tip. I did call him, he called me back, told him the issue, never heard from him again. I thought you should know. I called a Chimney Guy and it was determined through experiments within the house that I need a Heat Recovery Ventilator system installed.

 

[bluefleetwood]

First and foremost, thank you all for your tips. I have called a chimney veteran who pointed out that my house, being as new and tight as it is needs a Heat Recovery Ventilator. When we pulled the flue pipe apart from the boiler, and lit a match it immediately blew it out pulling air from the house. Then he told me to turn on the clothes dryer, one bathroom exhaust fan and the Range Hood on the floor above and we noticed reverse pressure. That was probably tripping out the Spill Switch which has been reinstalled in the vent. I am also assuming that reverse pressure was keeping the boiler from firing up as well. In the meantime, I have several windows in my basement by the boiler and have one of them cracked open about an inch with a screen on it until I can install the system. Does any of this make sense to you guys? Thanks again.

 

[NY_Rob]

Sorry Robert never followed up after his initial call... he's super busy I assume?

We also had really good results from "Soundview Heating & Air Conditioning" in Port Jefferson Station.
They did some work at the Firehouse in Riverhead- top notch workmanship.
I'd give them a call before installing a "Heat Recovery Ventilator".

 

[Dana]

A heat recovery ventilator (HRV) may or may not (usually not) provide enough make up air to get the flue to draft properly, but it'll mitigate against high concentrations of exhaust gases in your house and is a good thing to have in general. It's not cheap to retrofit a fully ducted HRV, but there are a few ductless versions (eg Lunos Nexxt, or E2) that might be easy enough as a DIY.

In tight houses it's sometimes necessary to install a large ducted make-up air vent from a basement window into the boiler room, with ducted air zone valve controlled to open whenever the flue damper opens to keep it from being a huge 24/7 air leak. That's not cheap either.

If fixing the drafting problems turns out to be very expensive it may be time to just retire the existing boiler early and replaced with for a RIGHT SIZED direct vented modulating condensing boiler. That's not cheap either, but at least it doesn't increase air leakage in to the house, saves on fuel costs, and reliably puts the exhaust outdoors. Most existing cast iron boilers on L.I. are 3x or more oversized for the actual heat load, often oversized for the radiation they're hooked up to. (A tight 2500' house in Setauket is likely to have a heat load of 30,000 BTU/hr or less, but still have a 100 KBTU/hr or larger boiler.) But it's possible to measure the heat load tracking the fuel use of the existing boiler against local weather data to figure out the approximate heat load.

 

[bluefleetwood]

A heat recovery ventilator (HRV) may or may not (usually not) provide enough make up air to get the flue to draft properly, but it'll mitigate against high concentrations of exhaust gases in your house and is a good thing to have in general. It's not cheap to retrofit a fully ducted HRV, but there are a few ductless versions (eg Lunos Nexxt, or E2) that might be easy enough as a DIY.

In tight houses it's sometimes necessary to install a large ducted make-up air vent from a basement window into the boiler room, with ducted air zone valve controlled to open whenever the flue damper opens to keep it from being a huge 24/7 air leak. That's not cheap either.

If fixing the drafting problems turns out to be very expensive it may be time to just retire the existing boiler early and replaced with for a RIGHT SIZED direct vented modulating condensing boiler. That's not cheap either, but at least it doesn't increase air leakage in to the house, saves on fuel costs, and reliably puts the exhaust outdoors. Most existing cast iron boilers on L.I. are 3x or more oversized for the actual heat load, often oversized for the radiation they're hooked up to. (A tight 2500' house in Setauket is likely to have a heat load of 30,000 BTU/hr or less, but still have a 100 KBTU/hr or larger boiler.) But it's possible to measure the heat load tracking the fuel use of the existing boiler against local weather data to figure out the approximate heat load.

What about installing a draft inducing fan into the flue?

 

[Dana]

Describe the flue & flue liner (if there's a flue liner), diameter of the liner if round, or if rectangular, XX" x YY", total height in feet from boiler port to top. Is it mostly interior to the house, or on an exterior wall?

What is the burner BTU rating on the boiler?

 

[bluefleetwood]

Describe the flue & flue liner (if there's a flue liner), diameter of the liner if round, or if rectangular, XX" x YY", total height in feet from boiler port to top. Is it mostly interior to the house, or on an exterior wall?

What is the burner BTU rating on the boiler?

I am pretty sure the flue is Terra cotta. Size I'm not sure sure of. I believe square and travels about 20-25 feet up the side of the house within a bricked chimney which has a separate Fireplace flue along side it.

 

[Dana]

"...up the side of the house..." means the brick is exposed to the exterior the whole way (or most of the way)?

117K-out/140K-in = 83.5% efficiency, and probably ~4x oversized for your space heating load, which means ~25% duty cycle even when it's +15F outside (your approximate 99% outside design temperature), and enough burner to heat your house down to an outdoor temp of -150F, provided you even have enough radiation to emit the full 117K, such as 225-250' of typical fin-tube baseboard. You probably don't have that much (do you?) not that you have much to worry about- it's been several ice ages and considerable continental drift since L.I. saw temps that low.

About how many square feet of house? How many feet of baseboard (by zone, if broken up into multiple zones)?

The low duty cycle and exterior chimney alone make it prone to backdrafting. If the flue is oversize for the 140KBTU/hr input it's even more true. With a 6" connector pipe with ~2-3' of lateral run and 20'+ of rise it really wants no larger than a 6" round flue liner or at most a 6x6 square terra cotta liner to have reasonable draft, and might even do better with a 5" liner.

With fan assist you can get there, but the fan becomes a significant parasitic heat load de-pressurizing the house, driving outdoor air infiltration whenever it's operating.

Spending money to make a ridiculously oversized boiler that's more than half way through it's service life work with poorly configured chimney is usually a waste of money. A fan assist would be a cheap way out in the short term, but that too needs to be specified, not hacked into working.

Run the numbers on the fuel use against heating degree days to come up with the range of likely load to check the oversizing factor. The raw combustion efficiency may be 83.5% but the as-used AFUE is probably less than 75% due to the standby losses wasted heating up the boiler room, and not quite heating up the flue sufficiently to draft well.

A cheap stainless fire-tube condensing boiler can fix all of these problems and allow you to retire the flue (is there a water heater hooked up to it?), and would likely reduce your wintertime gas bills by 30% or more, while keeping the place more comfortable. (Just ask NY_Rob!)

 

[bluefleetwood]

First thing... don't stack books right next to the boiler. They can burn. Please, observe 'setback' from combustibles.

What are the green and white wires that are hose clamped to the gas pipe?

I was wondering if the ignition control could be the problem? Or the gas valve?Could be...

Can you get us the gas valve information? model number, etc?

Do you own and know how to use a multimeter?
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Regards Jon Walter

Hi Jon, To which Green and White wires are you referring? I do use a multi meter as I am an Electrician. I am trying to see which pictures I've sent that have the wires you've mentioned.